System and method for controlled gas-dispersion-return-sludge-based wastewater treatment

ABSTRACT

Control over the wastewater purification can be achieved through controlling delivery of gas-dispersion return sludge solely to an aerobic reaction vessel. The gas-dispersion return sludge is created using pure oxygen or oxygen containing trace amounts of ozone as a reactive gas, which is blended with return sludge to create a mixture of gas and liquid, which is pressurized with an atomizer pump, and then at a pressure of not more than approximately 5.5 MPa, the mixture is passed through an atomizer which uses cavitation or ultrasound at a frequency of less than 12,000 KHz to instantly render the reactive gas in the mixture to an ultra-fine bubble state. A portion of the gas is placed into a dissolved state, reaching a state of supersaturation with a high DO value of 20-40 mg/l, and causing the remaining ultra-fine bubbles to create an ultra-fine bubble condition.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a continuation of U.S. patent applicationSer. No. 16/236,190, filed Dec. 28, 2018, pending, which is acontinuation of U.S. Pat. No. 10,167,214, issued Jan. 1, 2019, thedisclosures of which are incorporated by reference.

FIELD

The present invention relates in general to wastewater purification, andin particular, to a system and method for controlledgas-dispersion-return-sludge-based wastewater treatment.

BACKGROUND

The activated sludge process is a widely-practiced biochemicalwastewater treatment and oxidation process that employs microorganismsand oxygen to immobilize dissolved organic pollutant substances in thewastewater as activated sludge, which is partly decomposed into water(H₂O) and carbon dioxide (CO₂) for removal.

Several challenges are associated with the traditionalactivated-sludge-based wastewater treatments. For instance, thebiochemical cleansing of organic pollutant substances depends largely onthe quantity of microorganisms (return sludge), the density of themicroorganisms, and the degree of their activity. However, to increasethe quantity of microorganisms, their density, and their activity,increasing accordingly the supply of dissolved oxygen, which isessential to the microorganisms, is necessary. Without adequate supplyof dissolved oxygen, the wastewater treatment may not be effective.

The importance of the dissolved oxygen can be seen from the followingexample. In the activated sludge method, 1BOD (Biological Oxygen Demandquantity, mg/l) of organic pollutant is defined as the amount of organicpollutant which requires 1DO (mg/l) of dissolved oxygen (O₂) to bebroken down by microorganisms in a five-day period under normalatmospheric pressure at 20° C. Meanwhile, 1COD (Chemical Oxygen Demandquantity, mg/l) is defined similarly as the amount which requires 1DO(mg/l) of dissolved oxygen (O₂) to be broken down chemically in a30-minute-to-two-hour period under normal atmospheric pressure at 20° C.Accordingly, in wastewater treatment under the standard activated sludgemethod, the cleansing capacity achieved per 1DO (dissolved oxygen, mg/l)is no greater than “1BOD (Biological Oxygen Demand quantity, mg/l) ofpollutant”. Meanwhile, in the same way, “1COD (Chemical Oxygen Demandquantity, mg/l) of pollutant” also requires 1DO (mg/l) of dissolvedoxygen (O₎. In other words, to clean “1BOD of pollutant” and “1COD ofpollutant” requires 2DO (mg/l) of dissolved oxygen. Without thesufficient amount of oxygen, the effectiveness of the activated sludgewastewater treatment is significantly limited.

Further, the cleansing of wastewater depends fundamentally on theactivity of microorganisms (activated sludge), and is thus saddled withthe problem of the formation of excess sludge due to the excessivereproduction of these microorganisms, and technology to control thisexcess has not yet adequately been realized. In other words, themicroorganisms which are involved in the cleansing of wastewater areconstantly reproducing themselves and then perishing due toself-oxidization, hence controlling and managing the amount of sludgeproduced and the amount destroyed is extremely difficult, and the lackof this control and management is considered the critical problem of theactivated sludge method. As a result, the large quantities of excesssludge that form are concentrated, transported and incinerated or buriedin landfills, causing massive processing costs for the removal of excesssludge and emissions problems from the release of carbon dioxide duringincineration.

In addition, the control and management of the wastewater cleansingprocess in the activated sludge method involves numerous parameterswhich must be observed, with many observation items and observationfrequencies, and requires the daily accumulation of a huge amount ofdata. Furthermore, controlling and managing the treatment capacity ofthe microorganisms which form the basis of the cleansing process isdifficult, and even with the introduction of information technology,analyzing ever-more complicated data, deciding on countermeasures andinstructing staff present a heavy burden for wastewater treatment plantmanagers.

Existing technologies fail to adequately address these challenges. Forexample, a technique known as preliminary aeration exists to enhancewastewater treatment capacity, in which the return sludge is aerated inadvance, the sludge (microorganisms) is activated, and is pumped intothe aeration vessel. However, the incremental capacity achieved bypreliminary aeration is less than 30%. Because preliminary aeration hassuch low aeration efficiency, the cost is very high, such thatpreliminary aeration requires an additional 100% of the aeration cost.Due to the high cost to achieve an incremental capacity of only 30%,preliminary aeration is not cost-effective.

Similarly, another technique used today is long-term continuous aerationbubbling technology which uses bubbles of around 1 mm diameter, thequantity of dissolved oxygen merely reaches an unsaturated state of DOvalue 2 (mg/l), which is insufficient to bring about a large increase inmicroorganisms (return sludge).

Likewise, U.S. Pat. No. 7,105,092, issued Sep. 12, 2006, to KousukeChiba (“'092 patent”), the disclosure of which is incorporated byreference, discloses a sewage treatment process by whichactivated-sludge method comprising line atomizing treatment. Wastewateris introduced into the treatment line. The wastewater passes through theadjustment vessel and the sedimentation vessel where inorganic pollutantsubstances are removed. Subsequently, the wastewater enters theanaerobic reaction vessel where the wastewater is acted upon byanaerobic microorganisms. Subsequently, the wastewater enters theaerobic reactive vessel where organic matter within the wastewater isconverted into activated sludge by the action of aerobic microorganisms.After the conversion process in the aerobic reaction vessel, the treatedwastewater solution which has had the dissolved organic matter convertedinto activated sludge is sent together with the activated sludge to thesludge sedimentation vessel, and the supernatant water is expelled fromthe wastewater treatment system. The supernatant water may also besubjected to advanced treatment for further purification.

The '092 patent further discloses that a portion of the activated sludgewhich has settled in the sludge sedimentation vessel passes through thesludge intake pipe and is supplied respectively as return sludge to theadjustment vessel, sedimentation vessel, anaerobic reactive vessel,aerobic reactive vessel, and sludge sedimentation vessel to effectmultiple functionality for each of those vessels, and to enhance thetreatment capacity of the wastewater system while allowing the remainderof the activated sludge to undergo separate treatment as excess sludge.However, each vessel has an original function and role, and in manycases, adding activated return sludge which holds large quantities ofreactive gases (oxygen or oxygen with trace amounts of ozone) mayinterfere with those functions or roles, thus decreasing theeffectiveness of wastewater treatment.

Accordingly, there is a need for a way to increase control overactivated sludge-based wastewater purification, including optimizingamount of oxygen available for the biochemical reaction during thepurification.

SUMMARY

Control over the wastewater purification can be achieved throughcontrolling delivery of gas-dispersion return sludge solely to anaerobic reaction vessel. The gas-dispersion return sludge is createdusing pure oxygen or oxygen containing trace amounts of ozone as areactive gas, which is blended with return sludge to create a mixture ofgas and liquid, which is pressurized with an atomizer pump, and then ata pressure of not more than approximately 5.5 MPa, the mixture is passedthrough an atomizer which uses cavitation or ultrasound at a frequencyof less than 12,000 KHz to instantly render the reactive gas in themixture to an ultra-fine (bubble diameter less than 30 μm) bubble state.A portion of the gas is placed into a dissolved state, reaching a stateof supersaturation with a high DO value of 20-40 mg/l (dissolved oxygenvalue), and causing the remaining ultra-fine bubbles to create anultra-fine bubble condition in the gas-dispersion return sludge.

This approach is particularly beneficial in that wastewater treatmentcapacity is dramatically increased, because gas-dispersion return sludgeis supplied only to the aerobic reactive vessel (aeration vessel), andthe amount of return sludge (microorganisms) can be raised freely to theoptimal level.

Further, this approach is beneficial in that in addition to bringingabout a dramatic increase in wastewater treatment capacity throughactivating the microorganisms within the gas-dispersion return sludgewith reactive gas, the approach allows the effects of the increase intreatment capacity to be fixed and kept constant, by allowing theproduction and conditions of the gas-dispersion return sludge to befixed.

Through the use of the gas-dispersion return sludge, simply by raisingor lowering the key parameter of the treatment, which is the quantity ofgas-dispersion return sludge, the entire wastewater treatment system canbe controlled and managed. In particular, by supplying of gas-dispersionreturn sludge solely to the aerobic reactive vessel and by freelyincreasing the quantity of gas-dispersion return sludge (microorganisms)to the optimal quantity, the wastewater treatment capacity can beincreased dramatically. With the exception of the agitation function,traditional aeration through bubbling becomes unnecessary, makingpossible a reduction in size of the aerobic reactive vessel.

Further, expressing clearly and precisely each processing cost itembecomes possible: the degree of treatment of the wastewater, quantity ofexcess sludge production, and the treatment capacity of the entiresystem, thus minimizing the sum total of the wastewater treatment costs.

Further, by fixing the degree of activation of the microorganisms, whichis the critical problem in the activated return sludge method,controlling and managing the activity level of the microorganisms andthe quantity of the colonies becomes possible, that is, the quantity ofgas-dispersion return sludge, such that the degree of freedom of controland management of the wastewater treatment system is increased, andcontrol and management become easy and concise.

In addition, a synergistic effect occurs between the action of themicroorganisms which have been activated by the reactive gases in thegas-dispersion return sludge and the supply of gas-dispersion returnsludge having been increased to the optimal quantity, increasing thedegree of cleansing of the wastewater and the wastewater treatmentcapacity.

Regarding the as yet unsolved critical problem of the activated sludgemethod (the large amounts of excess sludge generated), by maintainingactivation with reactive gas (supersaturation with dissolved oxygenand/or trace amounts of ozone) at a sufficiently high level,simultaneously stimulating both the autonomous reproduction and theself-oxidation of the microorganisms (sludge) becomes possible. Further,by continuing the wastewater cleansing treatment process driven by themicroorganisms (activated sludge) in a stable fashion for a set periodof time, balancing the amount of sludge generated (quantity ofautonomous reproduction) with the autonomous extinction of the sludgedue to self-oxidation and stabilize the system becomes possible, suchthat by increasing and decreasing the quantity of return sludge, theproduction of excess sludge can be controlled and managed, and thequantity of return sludge generated can be reduced to a minimum (≈0).

Finally, as stated above, the system and method described simultaneouslysolve the problems of inefficient bubbling which attempts to useinsoluble air as a reactive gas through continuous aeration overextended periods (involving large operating costs and large facilitycosts for aeration), the problem that treatment with microorganismsrequires much time, and the problem that large quantities of excesssludge are generated, creating an enormous economic effect for theentire world. Further, as the centralization of population in the formof urbanization progresses rapidly on a global scale, the system andmethod can regenerate and revitalize as a low-cost, high-efficiencytechnology infrastructure for an energy-efficient city.

In one embodiment, a system and method for controlled gas-dispersionreturn-sludge-based wastewater treatment are provided. Wastewater ispumped into a sedimentation vessel, the wastewater including inorganicsolids and solid organic materials, wherein at least some of theinorganic solids settles from the wastewater in the sedimentationvessel. The wastewater is pumped from the sedimentation vessel into anadjustment vessel, the adjustment vessel including anaerobic organismsthat solubilize at least some of the solid organic materials within thewastewater. The wastewater is pumped from the adjustment vessel into oneor more aerobic reaction vessels in which the wastewater mixes with agas-dispersion return sludge to form a mixed liquor, the gas-dispersionreturn sludge including at least one reactive gas a portion of which isdissolved and a portion of which is in a state of ultra-fine bubbles,the gas-dispersion return sludge further including aerobicmicroorganisms that immobilize the solubilized organic materials withinthe mixed liquor as activated sludge using the at least one dissolvedreactive gas, wherein at least some of the ultra-fine bubbles dissolvewithin the mixed liquor upon a consumption of the dissolved portion ofthe reactive gases by the aerobic microorganisms. The mixed liquor ispumped from the one or more aerobic reaction vessels into a sludgesedimentation vessel in which the mixed liquor is separated into asupernatant and the activated sludge. The activated sludge is pumpedfrom the sludge sedimentation vessel into a sludge storage vessel. Atleast some of the activated sludge is pumped from the sludge collectionvessel to a line atomizer as a return sludge. At least one reactive gasis generated using a gas generator. The line atomizer is used to formthe gas-dispersion return sludge by rendering at least a portion of theat least one reactive gas generated by the gas generator into theultra-fine bubbles within the return sludge, wherein a portion of theultra-fine bubbles dissolves within the return sludge. User input isreceived by a controller interfaced to the sludge storage vessel, theline atomizer, and the gas generator, and an amount of thegas-dispersion return sludge pumped into the aerobic reaction vessel iscontrolled based on the user input. The gas-dispersion return sludge ispumped by the line atomizer under the control of the controller into theone or more aerobic reaction vessels.

By standardizing the equipment and keeping the gas-dispersed returnsludge reactive gas content fixed, the function and effect of theactivated microorganisms remains constant and fixed which allows controlof the waste water treatment process.

Still other embodiments of the present invention will become readilyapparent to those skilled in the art from the following detaileddescription, wherein is described embodiments of the invention by way ofillustrating the best mode contemplated for carrying out the invention.As will be realized, the invention is capable of other and differentembodiments and its several details are capable of modifications invarious obvious respects, all without departing from the spirit and thescope of the present invention. Accordingly, the drawings and detaileddescription are to be regarded as illustrative in nature and not asrestrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a system forgas-dispersion-return-sludge-based wastewater treatment in accordancewith one embodiment.

FIGS. 2(A)-2(B) are flow diagrams showing a method forgas-dispersion-return-sludge-based wastewater treatment in accordancewith one embodiment.

FIG. 3 is a flow diagram showing a routine for forming gas-dispersionreturn sludge and returning the gas-dispersion return sludge to theaerobic reaction vessel for use in the method of FIGS. 2(A)-2(B) inaccordance with one embodiment.

DETAILED DESCRIPTION

By using the quantity of gas-dispersion return sludge as a key parameterand delivering the gas-dispersion return sludge only to an aerobicreaction vessel, the system and method described below allow to easilyand compactly unitarily control and manage the degree of wastewatertreatment, the production quantity of excess sludge, and the wastewatertreatment capacity. Further, by stabilizing the production of thegas-dispersion return sludge, the system and method described belowallow to stabilize the activation effect of microorganisms within thegas-dispersion return sludge.

FIG. 1 is a block diagram showing a system 10 forgas-dispersion-return-sludge-based wastewater treatment in accordancewith one embodiment. The system includes as Sedimentation Vessel (alsoknown as a sediment pool and a grit chamber) 12, an Adjustment Vessel14, an Aerobic Reaction Vessel (also known as an aeration vessel) 16, aSludge Sedimentation Vessel 18, a Sludge Storage Vessel 20, an AtomizerPump 22, and an Atomizer 24.

In the description below, the phrase “Line Atomizer 29” is defined asthe combination of the Atomizer Pump 22 and the Atomizer 24.

In further detail, the Line Atomizer 29 signifies the entire line ofequipment which includes the Atomizer Pump 22, which has the function ofpumping vapor-liquid (liquid infused with vapor) with a vapor-to-liquidratio of up to 50% by volume at a pressure of approximately 0.981-5.394MPa (1-55 kg/cm², and the Atomizer 24, which has the function ofchurning and mixing the aforementioned vapor-liquid under high pressure(approximately 0.981-5.394 MPa (1-55 kg/cm²)), then employing eithercavitation or 20-12,000 kHz ultrasound respectively or bothsimultaneously to induce ultra-fine bubbles in the vapor-liquid ofdiameter from 1 nm-30,000 nm, further causing oxygen radicalization andhydroxyl radicalization.

The Sludge Storage Vessel 20 and the Aerobic Reaction Vessel 16 areconnected by the Return Sludge Pipeway 26, constructed such that returnsludge which has settled in the Sludge Storage Vessel 20 can be suppliedto the Aerobic Reaction Vessel 16. The Atomizer Pump 22 and the Atomizer24 are positioned linearly along the Return Sludge Pipeway 26. ReturnSludge 35 which travels through Return Sludge Pipeway 26 is thereforeacted on by the Atomizer Pump 22 and the Atomizer 24 and becomesgas-dispersion return sludge 36, which is in turn supplied to theAerobic Reaction Vessel 16 as gas-dispersion return sludge Z.

For the Atomizer Pump 22 and the Atomizer 24, the atomizer pump andatomizer in the U.S. Pat. No. 7,105,092 cited above, the disclosure ofwhich is incorporated by reference, may be utilized. In a furtherembodiment, other kinds of Atomizer Pump 22 and Atomizer 24 arepossible.

The system 10 further includes an Oxygen and Ozone Generator 28.

The Oxygen Supply Pipe 30 and the Ozone Supply Pipe 32 which areconnected to the Oxygen and Ozone Generator 28 are connected to a pipethat is part of a Return Sludge Pipeway 26 and is in the upstream(intake) side of Atomizer Pump 22.

For the Oxygen and Ozone Generator 28, the oxygen and ozone generator inU.S. Pat. No. 7,105,092 may be utilized.

The Return Sludge Pipeway 26 is connected only to the Aerobic ReactionVessel 16, and is therefore not connected to Sedimentation Vessel 12,Adjustment Vessel 14, and Sludge Sedimentation Vessel 18. Thetechnological reason for this is discussed below.

As further described below beginning with reference to FIGS. 2(A)-2(B),the Wastewater for Treatment (raw sewage) 11 enters Sedimentation Vessel12 where grit and other inorganic solids settle and are separated out.From the Sedimentation Vessel 12, the Wastewater 11 flows intoAdjustment Vessel 14 where the load and conditions of the inflowing rawsewage is adjusted, such as through automatic dilution, though otheradjustments are possible, and organic solids present in the wastewaterare solubilized by anaerobic microorganisms.

From the Adjustment Vessel 14, the Wastewater 11 flows into AerobicReaction Vessel 16 (aeration vessel), where gas-dispersion return sludge36 is added to the Wastewater 11 and blended to form a mixed liquor 17.From there, aeration by bubbling using air as a reactive gas becomesunnecessary due to the reactive gas contained in gas-dispersion returnsludge 36, which supplies dissolved oxygen (DO) to the Aerobic ReactionVessel 16, and causes residual organic solids within the mixed liquor 17left after the reaction involving the anaerobic microorganisms withinthe Adjustment Vessel 14 to be oxidized, and at the same timebiochemical treatment by aerobic microorganisms occurs, the dissolvedorganic pollutant substances in the mixed liquor 17 are immobilized asactivated sludge 21, and a portion of this activated sludge 21, isbroken down to water (H₂O) and carbon dioxide (CO₂) and removed.

Next, the mixed liquor progresses to Sedimentation Vessel 18, settlesinside Sedimentation Vessel 18 and is separated into sludge 21 andsupernatant. The settled activated sludge is collected in Sludge StorageVessel 20, and as described further below, is returned to AerobicReaction Vessel 16 in the form of gas-dispersion return sludge 36, forcyclical reuse.

Additionally, the excess sludge is pumped out of the wastewatermanagement system as Excess Sludge 38.

The density of gas-dispersion return sludge 36 is maintained at a fixedlevel. Gas-dispersion return sludge 36 is returned solely to AerobicReaction Vessel 16, and is not returned to Sedimentation Vessel 12,Adjustment Vessel 14, or Sludge Sedimentation Vessel 18. The returnedquantity of gas-dispersion return sludge 36 is unitarily controlled andunitarily managed to maximize the sum total reduction of carbon dioxide,the reduction in treatment costs, and the reduction in energy usage ofthe entire wastewater treatment system.

Because the wastewater treatment capacity of the Aerobic Reaction Vessel16 is dramatically increased, the Aerobic Reaction Vessel 16 can be madevery small.

The oxygen and ozone generated by the Oxygen and Ozone Generator 28 passrespectively through the Oxygen Supply Pipe 30 and the Ozone Supply Pipe32, then into the intake of the Atomizer Pump 22, and are blended insidethe Return Sludge Pipeway 26. Return Sludge 35 with gases mixed in ispumped by the Atomizer Pump 22, and when the Return Sludge 35 with gasesmixed in passes through the Atomizer 24, the reactive gases aredissolved and stored in the return sludge instantaneously (within 0.5seconds) to form gas-dispersion return sludge 36. After this, themixture is supplied to the Aerobic Reaction Vessel 16 as gas-dispersionreturn sludge 36. The use of the supplied gas-dispersion return sludge36 has been supplied to Aerobic Reaction Vessel 16 is as has beendescribed above.

Further, the production of the Excess Sludge Y is ideally minimized(≈0). In doing so, the disposal cost of Excess Sludge Y can be greatlyreduced.

As the Line Atomizer 29 can instantaneously render the desired quantityof reactive gas into ultra-fine bubbles, rapidly dissolving a portion ofthe reactive gas, then disperse, immobilize and store the excess in aliquid in the form of ultra-fine bubbles, the Line Atomizer 29 cancreate a liquid in which gas is dispersed, immobilized and stored(gas-infused liquid) which can be suitably returned or supplied to theaeration treatment process in an easily utilized dissolved state orultra-fine bubble state.

Regarding the slowing effect on the velocity at which bubbles risewithin a liquid which can be achieved by producing bubbles which areultra-fine, bubbles with diameter of around 30 μm rise within a liquidat approximately 1 m/hr, and at a diameter of around 1 μm they rise atless than 0.005 m/hr (Stokes' Law for Spherical Bubbles). With thisrange of velocity, bubbles remain within the liquid for long enough thatthey can immediately and at the required position replace dissolvedoxygen which has been consumed by the biochemical reaction with thepollutant substances in the wastewater to be treated, and furthermore,because the bubbles can be dispersed in ultra-fine bubble form,uniformly and in great quantity, and therefore in the same places whereoxygen has been consumed, a bubble storage function is also achieved.

In this way, the desired reactive gases including oxygen or oxygen andozone can be supplied and stored with extremely long duration, withneither surplus nor shortage, thereby shortening and stimulating thebiochemical reaction, and also allowing that the supply within the timeperiod required to carry out the biochemical reaction need notnecessarily be continuous but can be intermittent.

As mentioned above, the Line Atomizer 29 is employed to disperse gasinto liquid in the form of ultra-fine bubbles. To render bubbles to anultra-fine size and blend the ultra-fine bubbles into liquid, mechanicalagitation and cutting are insufficient to achieve the nano level, andonly when the velocity of the two-phase flow of the vapor-liquid isincreased through pressurization, and a synergistic effect with thevortex churning of the liquid is generated using cavitation andultrasound, that the bubbles are broken down to ultra-fine state andblended into the mixture as ultra-fine bubbles. For the gas to bedissolved and remain in dissolved state, pressure conditions are of keyimportance, and higher pressures are known to be more advantageous.Taking all these factors into account, the range of pressure chosen forthe Line Atomizer 29 is from 0.1 MPa-5.394 MPa (1-55 kg/cm²).

In a simple return process for activated sludge (with zero addition ofreactive gas), operating in low pressure ranges to avoid destroying themicroorganisms which exist in the activated sludge. Further, the reasonto strive for the highest pressure that can be practically achieved(approximately 5.5 MPa), is to effectively utilize, in the oxidation anddecomposition process of sludge employing reactive gas including highdensity ozone, a synergistic oxidation and decomposition effect betweenthe actions of cavitation and ultrasound, which under high pressurecause the oxidation and breakdown of ozone itself, and the functioningof O radicals and OH radicals. With the large-capacity wastewatertreatment employing the activated sludge method of the system 10, carehas been taken to choose frequencies of ultrasound which can be usedeasily and economically, and so at low pressure ranges a frequency of 20kHz was chosen, and for high pressure ranges (approximately 5.5 MPa) afrequency range of 12,000 kHz was chosen.

For the Oxygen and Ozone Generator 28, an ozone generator or similar maybe used to regulate the supply of oxygen and the generation of ozone.For example, by employing an ozone-generating element comprising anelectrode mounted to a dielectric substance, and a high-frequencyhigh-voltage power source which applies a high-frequency alternatingcurrent to the ozone-generating element while supplying an oxygen-richgas to the ozone-generating element, and adjusting the quantity of ozonegenerated by using a regulator to control the voltage and/or thefrequency of the power source, it becomes possible to effect anoxygen/ozone cycle generator which regulates the amount of oxygen andozone supplied, to cope with fluctuations in the quality and load ofsewage for wastewater treatment due to morning, daytime or nighttime, ordue to either dry weather or rainy weather, or to cope with processesbased mainly on the supply of oxygen and with processes based mainly onoxidation and decomposition by ozone. For the reactive gas includingoxygen to be supplied, air, oxygen-enriched air, or pure oxygen are allacceptable. The supplied gas may also be pumped as is, with zero ozonegeneration. Of course, the operation of the oxygen/ozone cycle generatormay also be suspended.

In the activated sludge process, the microorganisms which effect thebiochemical reaction are returned to the wastewater intake side with aportion of the sludge (return sludge) such that the microorganisms areutilized cyclically. If the wastewater 11 to be treated is wastewater 11which includes high densities of organic substances, and acceleratingthe microbial biochemical reaction is therefore necessary, thenmaximizing the quantity of oxygen dissolved in the wastewater 11 orreplenishing dissolved oxygen rapidly according to the amount ofdissolved oxygen which is consumed is desirable. The system 10 performsfavorably in this respect, employing the Line Atomizer 29 to infuse withthe required amount of oxygen gas (or oxygen with the trace of ozone)the water which carries the return sludge back to Aerobic ReactionVessel 16. The microbial biochemical reaction is accelerateddramatically due to the Line Atomizer 29 supplying a plentiful amount ofoxygen (or oxygen with a trace of ozone) in a dissolved state and in theform of ultra-fine bubbles in an extremely short time.

Because ultra-fine bubbles, as previously described, require a very longtime to float to the surface of Aerobic Reaction Vessel 16, during thetime which it takes them to float to the surface of Aerobic ReactionVessel 16, the ultra-fine bubbles in Aerobic Reaction Vessel 16 aredispersed and stored in the form of ultra-fine bubbles, and continuouslyreplenish the dissolved oxygen. By maintaining a high quantity ofdissolved oxygen in Aerobic Reaction Vessel 16, significant accelerationof the microbial biochemical reaction becomes possible. Due to theeffect of the microbial biochemical reaction within Aerobic ReactionVessel 16, a portion of the organic matter in the wastewater isdigested, releasing carbon dioxide and water, and a portion of theorganic matter is consumed by activated sludge microorganisms; themicroorganisms multiply, and the activated sludge is generated. In thiscase, by adding not only oxygen to the wastewater, but by also addingand employing trace amounts (e.g. up to 0.01-0.4 mg/l=ppm) of ozone,activating the microorganisms which carry out the microbial biochemicalreaction becomes possible.

The amount of gas-dispersion return sludge 36 that is provided by theLine Atomizer 29 into the Aerobic Reaction Vessel 16 is a key parameterfor controlling the purification of the wastewater 11 treatment. Inparticular, the following characteristics of the wastewater treatmentcan be directly controlled and managed through increasing or decreasingthe gas-dispersion return sludge:

1) Degree of wastewater treatment: the degree of treatment can beheightened by increasing the amount of gas-dispersion return sludge(quantity of reactive gas and microorganisms);

2) Wastewater treatment time: the treatment time can be shortened byincreasing the amount of gas-dispersion return sludge (quantity ofmicroorganisms); and

3) Wastewater treatment capacity: the capacity can be increased byincreasing the amount of gas-dispersion return sludge (quantity ofmicroorganisms).

As the properties of the gas-dispersion return sludge 36 are fixed bythe functional limitations of the equipment employed, their activationcapacity (activation effect) becomes fixed and is not a parameter. Inmore detail, oxygen or oxygen with trace amounts of ozone is used as areactive gas, it is blended into the return sludge which is sent toAtomizer Pump (liquid-vapor pressuring pump) 22, and by passing throughAtomizer 24, a portion of the reactive gas is instantaneously dissolvedinto the return sludge 35 and the remainder is stored in the form ofultra-fine bubbles creating “gas-dispersion sludge”. This gas-dispersionsludge contains dissolved oxygen DO in super-saturated state (DO value20-40 mg/l) and in particular trace amounts of ozone (0.01-0.4 mg/l).For this reason, the gas-dispersion return sludge maintains a state ofextremely high activation, and the microorganisms within thegas-dispersion return sludge are further activated by the highactivation properties of the reactive gas. In this way, thegas-dispersion return sludge is employed such that its properties andfunction are fixed, so effect of the gas-dispersion return sludge 36 isalso fixed. In other words, the effect becomes a constant rather than avariable and can therefore be excluded from the control items.

In one embodiment, the components of the system 10 described above canbe controlled independently of each other. In a further embodiment, thesystem 10 includes a Controller 39 that is interfaced, such as via awired or a wireless connections, to at least the Sludge SedimentationVessel 20, the Oxygen and Ozone generator 28, and the Line Atomizer 29.The Controller 39 can also be similarly interfaced to other componentsof the system 10. The Controller 39 can receive from a user the amountof gas-dispersion return sludge 36 that is to be delivered to theAerobic Reaction Vessel 16 and control the Sludge Sedimentation Vessel,the Oxygen and Ozone Generator 28, and the Line Atomizer 29 to deliverthe desired amount of the gas-dispersion return sludge 36.Alternatively, the controller 39 can receive from a user acharacteristic of the wastewater treatment, such as a degree of thewastewater treatment desired by the user, a wastewater treatment timedesired by the user, and a desired wastewater treatment capacity, anddetermine the amount of the gas-dispersion return sludge 36 to bedelivered to the Aerobic Reaction Vessel 16 to achieve the desiredcharacteristic. The determined amount can then be delivered under thecontrol of the Controller 39. The Controller 39 can be a computingdevice, such as a personal computer, a smartphone, a laptop, a tablet,though other kinds of computing devices are possible. The Controller 39can include components conventionally found in general purposeprogrammable computing devices, such as a central processing unit,memory, input/output ports, network interfaces, and non-volatilestorage, although other components are possible. The central processingunit can implement computer-executable code which can be implemented asmodules. The modules can be implemented as a computer program orprocedure written as source code in a conventional programming languageand presented for execution by the central processing unit as object orbyte code. Alternatively, the modules could also be implemented inhardware, either as integrated circuitry or burned into read-only memorycomponents. The various implementations of the source code and objectand byte codes can be held on a computer-readable storage medium, suchas a floppy disk, hard drive, digital video disk (DVD), random accessmemory (RAM), read-only memory (ROM) and similar storage mediums. Othertypes of modules and module functions are possible, as well as otherphysical hardware components.

The Controller 39 can be controlled by a user on-site or remotely. Forexample, the Controller 39 can be interfaced to an Internetwork, such asthe Internet or a cellular network, and a user device (such as asmartphone though other user devices are possible) also interfacedallows to command the Controller 39 remotely, and provides remotecontrol of the system 10 to a user.

Other kinds of the Controller 39 are also possible.

When the system 10 has not recently been ran, there may not alwaysgas-dispersion return sludge 36 available to be added to the AerobicReaction Vessel 36 and provide the aerobic microorganisms necessary toconduct the aerobic reaction to the Aerobic Reaction Vessel. In such asituation, the system 10 may utilize seed sludge—activated sludge 21that is input into the system 10, such as into the Return Sludge Pipeway26, from an external source, such as another wastewater treatmentsystem, though other external sources are possible. By being processedby the Line Atomizer 29 and the Oxygen and Ozone Generator 28, the seedsludge is turned into the gas-dispersion return sludge 36 and can thenbe provided to the Aerobic Reaction Vessel 16 to be used for thetreatment of the wastewater 11. As the microorganisms present inactivated sludge 21 differ significantly based on the geographic originof the wastewater 11 from which the sludge 21 is created, the seedsludge introduced into the system 10 is selected based on the geographiclocation of the wastewater from 21 from the seed sludge originates.Preferably, the seed sludge is from the same or proximate geographiclocation as the wastewater 11 being processed by the system 10 to avoidan introduction of exogenous microorganisms that can negatively impactthe aerobic reaction.

While the description above references the system 10 including a singleAerobic Reaction Vessel 16, in a further embodiment, multiple AerobicReaction Vessels 16 can be included in the system 10, with thegas-dispersion return sludge 36 being provided into all of the Vessels16.

As described above, providing the gas-dispersion return sludge 36 allowsto exercise increased control over the wastewater purification. FIGS.2(A)-2(B) are flow diagrams showing a method 40 forgas-dispersion-return-sludge-based wastewater treatment in accordancewith one embodiment. The method can be implemented using the system 10of FIG. 1. Optionally, if no gas-dispersion return sludge 36 is presentin the Aerobic Reaction Vessel at the start of the execution of themethod 40, seed sludge is added to the system 10, is converted intogas-dispersion return sludge 36, and is provided into the AerobicReaction Vessel, as described above with reference to FIG. 1 (step 41).The load of wastewater 11 to be treated is determined (step 42) and theamount of gas-dispersion return sludge 36 to be delivered to the AerobicReaction Vessel 16 is determined (step 43). The determination can bedone based on the load as well as other desired characteristics of thewastewater treatment, such as the degree of the purification and thespeed of the treatment, though other characteristics are possible.

The wastewater 11 enters Sedimentation Vessel 12 where grit and otherinorganic solids settle and are separated out (step 44). Subsequently,the wastewater 11 enters Adjustment Vessel 14 where the load andconditions of raw sewage 11 are adjusted and solid organic material issolubilized by anaerobic microorganisms (step 45).

Next, the wastewater 11 flows into one or more Aerobic Reaction Vessels16, where the wastewater 11 (raw sewage) is added to gas-dispersionreturn sludge 36 and blended to form mixed liquor 17 (step 46). Fromthere, if any aeration by bubbling using air as a reactive gas waspreviously performed, such aeration becomes unnecessary due to thereactive gas contained in gas-dispersion return sludge 36. Dissolvedoxygen (DO) is supplied to the Vessel 16 by the gas-dispersion returnsludge 36 and organic solids left undissolved after step 45 areoxidized; at the same time biochemical treatment by aerobicmicroorganisms occurs, with the organic pollutant substances dissolvedin the in the wastewater 11 being immobilized as activated sludge 21,and a portion of this activated sludge 21 is broken down to water (H₂O)and carbon dioxide (CO₂) and removed (step 47).

Next, the mixed liquor 17 progresses to Sedimentation Vessel 18, settlesinside Sedimentation Vessel 18 and is separated into sludge andsupernatant (step 48). The settled activated sludge is collected inSludge Storage Vessel 20 (step 49), and is returned to Aerobic ReactionVessel 16 in the form of gas-dispersion return sludge 36, for cyclicalreuse (step 50), as further described below with reference to FIG. 3.Excess sludge 27 is expelled from the Sludge Collection Vessel and fromthe system 10 (step 51). If more wastewater 11 to be treated remains(step 52), whether the amount of solid pollutants, organic andinorganic, in the next batch of wastewater 11 to be treated requiresaction via execution of steps 44 and 45 is determined (step 53). Thedetermination can be made by comparing the level of the solids to one ormore thresholds, though other kinds of determinations are possible. Ifthe level requires action (step 53), the method returns to step 44. Ifthe level does not require action, the method 40 returns to step 46. Ifthe no more wastewater 11 remains to be processed (step 52), the method40 ends.

Providing the gas-dispersion return sludge 36 solely into the AerobicReaction Vessel 16 allows to achieve an optimum quantity of the aerobicmicroorganisms within the Aerobic Reaction Vessel 16. FIG. 3 is a flowdiagram showing a routine for forming gas-dispersion return sludge andreturning the gas-dispersion return sludge 36 to the aerobic reactionvessel for use in the method of FIGS. 2(A)-2(B) in accordance with oneembodiment.

Reactive gas, pure oxygen or oxygen containing trace amounts (0.01-0.4mg/l) of ozone, is generated by the Oxygen and Ozone Generator 28 (step61). As described above, the Atomizer Pump 22 and the Atomizer 24 areinstalled along the Return Sludge Pipeway 26, and the reactive gas isintroduced into the intake side of Atomizer Pump 22 and the returnsludge 35 is converted into a gas-liquid mixed liquor (step 62). Thisgas-liquid mixed liquor (sludge) is pumped by the Atomizer Pump 22 andin passing through the Atomizer 24, the reactive gas within thegas-liquid mixed liquor (gas-dispersion sludge) is instantaneously(within 0.5 seconds) rendered into ultra-fine bubbles (bubble diameterless than 30 μm, ideally bubble diameter less than 1 μm) and a portionof it is instantly dissolved (step 63). With this, a super-saturated DOvalue of 20-40 mg/l is realized, and the remaining gas is dispersed,immobilized and stored within the sludge in an ultra-fine bubble state.

This gas-dispersion return sludge containing reactive gas is supplied bythe Atomizer only to the one or more Aerobic Reaction Vessels 16, whereis blended with wastewater 11 to be treated, forming a mixed liquor(step 64), ending the routine 60.

As mentioned above, upon addition of the gas-dispersion return sludge toone or more of the Reaction Vessels that point, any bubbling in theAerobic Reaction Vessel 16 can be ceased. Or, in cases where thebubbling is required to prevent the settling of sludge, bubblingaeration can be minimal and may be conducted intermittently and forshort periods of time. As a result, the holding period in AerobicReaction Vessel 16 can be reduced to a fraction equal to 1 divided bythe number of Aerobic Reaction Vessels 16. In other words, if there arefour Aerobic Reaction Vessels 16, the holding period would be reduced to¼ of the current holding period. Three of the four Aerobic ReactionVessels 16 will no longer be required.

Further, by increasing the amount of return sludge, the rate of reactionis increased and enhanced, and the holding period within the aerobicreaction vessel can be reduced even further. The microorganisms areactivated by the reactive gas contained within the return sludge, anddue to the synergistic effect of increasing the quantity ofgas-dispersion return sludge, purification capacity is increased by amultiple of around 25-40.

Furthermore, through the activation of the microorganisms (sludge), boththe autonomous reproductive function and the self-oxidation function canbe made more active. By continuing the wastewater purification processof the microorganisms (activated sludge) in a stable fashion for a setperiod of time, the production of sludge (autonomous reproduction) andthe extinction of sludge due to self-oxidation can be held in balanceand maintained regularly and constantly.

Through the control and management of the above wastewater purificationsystem, taking the returned quantity of gas-dispersion return sludge 36as the Key Parameter, since the parameter is constructed in acomprehensively simple and compact fashion, identifying and clarifyingthe reduction in carbon dioxide, the reduction in treatment cost, andthe improvement in energy savings of the entire wastewater treatmentsystem becomes simple.

Further, if a wastewater treatment facility (e.g. a sewage treatmentplant) using the system 10 and method 40 for wastewater purificationwere to be newly constructed, the Sedimentation Vessel 12, an anaerobicreaction vessel (which also doubles as Adjustment Vessel 14), and theAerobic Reaction Vessel 16 may all be built as one unit. The volume ofAerobic Reaction Vessel 16 may be decided based on a standard holdingperiod of about two hours. However, since the quantity of gas-dispersionreturn sludge 36 can be selected freely depending upon the load andconditions of the wastewater 11 to be treated (raw sewage) within therange of 20-300% of the volume of the wastewater 11, when calculatingthe volume of wastewater 11 adding in the amount of gas-dispersionreturn sludge 36 to be returned is necessary. Also, the volume of SludgeSedimentation Vessel 18 should be determined in the same way as AerobicReaction Vessel 16.

In the system 10 and method 40, the conditions and load of wastewater tobe treated are determined and fixed. So, by fixing the microorganismdensity of the gas-dispersion return sludge 36, controlling and managingthe wastewater treatment process solely by increasing or decreasing thequantity of gas-dispersion return sludge 36 returned to Aerobic ReactionVessel 16. In other words, to achieve the ideal quantity ofgas-dispersion return sludge 36 for the load and conditions of theentering wastewater, the quantity of gas-dispersion return sludge 36 canbe increased or decreased freely within the range of 20-300% of thevolume of the wastewater 11. By increasing or decreasing the amount ofthe return sludge 36 added to the Aerobic Reaction Vessel 16, an almostcomplete purification of the Wastewater can be achieved, with almostzero of the undesired pollutants being present following thepurification.

Further, the more the quantity of gas-dispersion return sludge 36 isincreased, the greater the degree of purification and the higher thetreatment capacity will be. However, if a greater than necessaryquantity of gas-dispersion return sludge 36 is used, the treatment costwill also rise. Therefore, the ideal quantity of gas-dispersion returnsludge 36 is identified and clarified to match the desired degree ofwastewater treatment.

Theoretically, the more the quantity of gas-dispersion return sludge 36is increased, the greater the degree of purification and the higher thetreatment capacity will be. However, if a greater than necessaryquantity of gas-dispersion return sludge 36 is used, the treatment costwill also rise. Therefore, if the quantity of gas-dispersion returnsludge 36 is gradually raised until the desired degree of wastewatertreatment is achieved, the minimum requisite quantity of gas-dispersionreturn sludge 36 can be identified and clarified.

At first, the quantity of gas-dispersion return sludge 36 is maintainedat a set level, and regular continuous operation should be carried outover a set period (around 4-6 weeks) to stabilize the wastewatertreatment system. At that time, the quantity of sludge generated isobserved. Once the wastewater treatment system has stabilized, thequantity of gas-dispersion return sludge 36 is increased or decreased,the change in sludge production is ascertained, and the quantity ofreturned sludge is adjusted to minimize sludge production. Bymaintaining the quantity of return sludge that minimizes sludgeproduction is maintained, and continuing operation to stabilize thetreatment system, the quantity of sludge generated and the quantity ofsludge returned can be balanced and the production of excess sludge canbe suppressed and controlled.

Thus, maximizing the reduction in wastewater treatment cost becomespossible.

While the invention has been particularly shown and described asreferenced to the embodiments thereof, those skilled in the art willunderstand that the foregoing and other changes in form and detail maybe made therein without departing from the spirit and scope of theinvention.

What is claimed is:
 1. A system for controlledgas-dispersion-return-sludge-based wastewater treatment, comprising: asedimentation vessel into which wastewater comprising inorganic solidsand solid organic materials is pumped and in which at least some of theinorganic solids settles from the wastewater; an adjustment vessel intowhich the wastewater from the sedimentation vessel is pumped and whichcomprises anaerobic organisms that solubilize at least some of the solidorganic materials within the wastewater; one or more aerobic reactionvessels into which the wastewater from the adjustment vessel is pumpedand in which the wastewater pumped from the adjustment vessel mixes witha gas-dispersion return sludge to form a mixed liquor, thegas-dispersion return sludge comprising at least one reactive gas aportion of which is dissolved and a portion of which is in a state ofultra-fine bubbles, the gas-dispersion return sludge further comprisingaerobic microorganisms that immobilize the solubilized organic materialswithin the mixed liquor as activated sludge using the at least onedissolved reactive gas, wherein at least some of the ultra-fine bubblesdissolve within the mixed liquor upon a consumption of the dissolvedportion of the reactive gases by the aerobic microorganisms; a sludgesedimentation vessel into which the mixed liquor is pumped from the oneor more aerobic reaction vessels and in which the mixed liquor isseparated into a supernatant and the activated sludge; a sludge storagevessel into which the activated sludge from the sludge sedimentationvessel is pumped, wherein at least some of the activated sludge from thesludge collection vessel is pumped to a line atomizer as a returnsludge; a gas generator configured to generate the at least one reactivegas; the line atomizer configured to form the gas-dispersion returnsludge by rendering at least a portion of the at least one reactive gasgenerated by the gas generator into the ultra-fine bubbles within thereturn sludge, wherein a portion of the ultra-fine bubbles dissolveswithin the return sludge, the line atomizer further configured to pumpthe gas-dispersion return sludge into the aerobic reaction vessel; and acontroller interfaced to the sludge storage vessel, the line atomizer,and the gas generator, the controller configured to receive user inputand to control an amount of the gas-dispersion return sludge pumped intothe one or more aerobic reaction vessels based on the user input.
 2. Asystem according to claim 1, wherein the user input comprises one ormore of a desired degree of purification of the wastewater, a desiredspeed of purification of the wastewater, and an amount of the wastewaterto be purified.
 3. A system according to claim 1, wherein the user inputcomprises the amount of the gas-dispersion return sludge to be pumpedinto the aerobic reaction vessel.
 4. A system according to claim 1,wherein the controller is interfaced to the sludge storage vessel, theline atomizer, and the gas generator via at least one of wirelessconnections and wired connections.
 5. A system according to claim 1,further comprising: a user device interfaced to the controller via anInternetwork and configured to provide the user input to the controllervia the Internetwork.
 6. A system according to claim 5, wherein theInternetwork comprises at least one of the Internet and a cellularnetwork.
 7. A system according to claim 1, wherein user input isprovided into the controller on-site.
 8. A system according to claim 1,wherein the at least one reactive gas comprises one or more of oxygenand ozone.
 9. A system according to claim 8, wherein the gas-dispersionreturn sludge comprises 0.01-0.4 mg/l of the ozone and 20-40 mg/l of theoxygen.
 10. A system according to claim 1, wherein the ultra-finebubbles are of a diameter less than 30 μm.
 11. A method for controlledgas-dispersion-return-sludge-based wastewater treatment, comprising:pumping into a sedimentation vessel wastewater comprising inorganicsolids and solid organic materials, wherein at least some of theinorganic solids settles from the wastewater in the sedimentationvessel; pumping from the sedimentation vessel the wastewater into anadjustment vessel, the adjustment vessel comprising anaerobic organismsthat solubilize at least some of the solid organic materials within thewastewater; pumping the wastewater from the adjustment vessel into oneor more aerobic reaction vessels in which the wastewater mixes with agas-dispersion return sludge to form a mixed liquor, the gas-dispersionreturn sludge comprising at least one reactive gas a portion of which isdissolved and a portion of which is in a state of ultra-fine bubbles,the gas-dispersion return sludge further comprising aerobicmicroorganisms that immobilize the solubilized organic materials withinthe mixed liquor as activated sludge using the at least one dissolvedreactive gas, wherein at least some of the ultra-fine bubbles dissolvewithin the mixed liquor upon a consumption of the dissolved portion ofthe reactive gases by the aerobic microorganisms; pumping the mixedliquor from the one or more aerobic reaction vessels into a sludgesedimentation vessel in which the mixed liquor is separated into asupernatant and the activated sludge; pumping the activated sludge fromthe sludge sedimentation vessel into a sludge storage vessel; pumping atleast some of the activated sludge from the sludge collection vessel toa line atomizer as a return sludge; generating using a gas generator theat least one reactive gas; forming using the line atomizer thegas-dispersion return sludge by rendering at least a portion of the atleast one reactive gas generated by the gas generator into theultra-fine bubbles within the return sludge, wherein a portion of theultra-fine bubbles dissolves within the return sludge; receiving userinput by a controller interfaced to the sludge storage vessel, the lineatomizer, and the gas generator, and controlling by the controller anamount of the gas-dispersion return sludge pumped into the aerobicreaction vessel based on the user input; and pumping using the lineatomizer under the control of the controller the gas-dispersion returnsludge into the one or more aerobic reaction vessels.
 12. A methodaccording to claim 11, wherein the user input comprises one or more of adesired degree of purification of the wastewater, a desired speed ofpurification of the wastewater, and an amount of the wastewater to bepurified.
 13. A method according to claim 11, wherein the user inputcomprises the amount of the gas-dispersion return sludge to be pumpedinto the aerobic reaction vessel.
 14. A method according to claim 11,wherein the controller is interfaced to the sludge storage vessel, theline atomizer, and the gas generator via at least one of wirelessconnections and wired connections.
 15. A method according to claim 11,further comprising: providing the user input to the controller by a userdevice via an Internetwork.
 16. A method according to claim 15, whereinthe Internetwork comprises at least one of the Internet and a cellularnetwork.
 17. A method according to claim 11, wherein user input isprovided into the controller on-site.
 18. A method according to claim11, wherein the at least one reactive gas comprises one or more ofoxygen and ozone.
 19. A method according to claim 18, wherein thegas-dispersion return sludge comprises 0.01-0.4 mg/l of the ozone and20-40 mg/l of the oxygen.
 20. A method according to claim 11, whereinthe ultra-fine bubbles are of a diameter less than 30 μm.